Mika/refactoring

New structure including soap_builder that extends itself with bank-specific modules

New features:
* Support for downloading Danske Bank certificates through wsdl

Parameter changes:
* Changed parameter => 'private_key:', now 'private_key_path:' containing path to local private key file OR 'private_key_plain' containing private key in plain text format
* Changed parameter => 'cert:', now 'cert_path:' containing path to local certificate file OR 'cert_plain:' containing certificate in plain text format
* Changed parameter => 'csr:', now 'csr_path:' containing path to local csr file OR 'csr_plain:' containing csr in plain text format
* New parameter => 'bank:', contains target bank as symbol
* New parameter => 'bank_root_cert_serial:', containing target serial number for Danske bank certificate download
* Removed parameter => 'wsdl:', now comes automatically from the gem depending on the param 'bank:' and param 'command:'

NOTE: Some unit tests might be redundant for now, this will be addressed later
NOTE: Removed features that do not function at this time because of encryption issues with Danske PKI
NOTE: Should support usage through sepa-api, this is however not guaranteed or tested